A flame-resisting insulation sheet has a thickness of from about 0.1 to 0.5 mm and is required to have superior heat resistance as well as superior flame-resisting and insulation properties. As such a flame-resisting insulation sheet, a polyvinyl chloride resin-made sheet has been used extensively. However, a flame-resisting insulation sheet comprising no halogen has been increasingly required, because of an environmental problem due to the influence of halogen contained in the resin. In addition, a thin sheet such as a flame-resisting insulation sheet, when burned, easily causes an undesirable phenomenon such that a kindling piece of the sheet drips, the phenomenon being hereinafter referred to as "dripping phenomenon". In this regard, a halogen-free sheet causes the dripping phenomenon more easily than a halogen-containing sheet.
As a technique to improve the dripping phenomenon of a polyphenylene ether resin, for example, U.S. Pat. Nos. 4,107,232, 4,332,714 and 4,355,126 disclose a combination use of polyfluoroethylene. Each of the references referred to above is incorporated herein by reference in its entirety.
However, there is left an environmental problem, because polyfluoroethylene also contains a halogen (fluorine) like a polyvinyl chloride resin.